Zoom lenses



A. COX ETAL July 17, 1962 ZOOM LENSES 6 AV v 4/ 1 t e e h S s t e e h s2 1 6 9 l 5 2 y a M d e l 1 F laznzors; @Yrfhur Cox Walter cfclviznsonA. COX ETAL July 17, 1962 ZOOM LENSES 2 Sheets-Sheet 2 Filed May 25.1961 III/anions: @(TZ/Eur Zl/aiier GIG/071726072 Cox United StatesPatent Office 3,044,355 Patented July 17, 1962 3,044,355 ZOOM LENSESArthur Cox, Park Ridge, and Walter J. Johnson, Mundelein, Ill.,assignors to Bell & Howell Company, Chicago, Ill., a corporation ofIllinois Filed Way 25, 1961, Ser. No. 112,721 2 Claims. (Cl. S8-57) Thisinvention relates to zoom lenses, and more particularly to zoom lenseshighly corrected over a large range of magnification.

An object of the invention is to provide a zoom lens highly correctedover a large range of magnification.

Another object of the invention is to provide an inexpensive zoom lenshighly corrected over a magnification range of at least three to one.

Another object of the invention is to provide a zoom lens highlycorrected over a magnification range of four to one.

It is to be understood that the terms front and rear" as herein usedrefer to the ends of the objective respectively nearer the long andshort conjugates thereof.

In the accompanying drawings forming a part hereof, FIGS. 1 and 2illustrate zoom lenses described herein and embodying the invention, andrespectively show the objective in the long variable equivalent focallength adjustments thereof.

The invention provides a zoom lens or variable equivalent focal lengthobjective having a front positive member, an intermediate negativemember and a rear positive member. The front positive member is movablenonlinearly during zooming and preferably is adjustable for focusingalso. The intermediate negative member is movable linearly for zooming,and the rear member is fixed. Preferably, the front member includes afront positive doublet and a rear positive singlet, the intermediatenegative member has a front negative meniscus singlet and a biconcaverear doublet, and the rear member comprises a rear prime lens group anda front singlet separated by a stop from the prime lens group andforming an afocal system with the front and intermediate members. Theafocal system preferably is undercorrected for astigmatism and the primelens group is overcorrected for astigmatism to balance out the residualastigmatism of the afocal system.

Referring now in detail to the drawings, the zoom lens shown thereinincludes a front lens member 1 (FIG. 1), an intermediate lens member 2and a rear lens member made up of a component or member 3 and a primelens or member 4 with a stop 5 positioned between the members 3 and 4.The members 3 and 4 are stationary or fixed, and, during zooming, themember 1 is moved nonlinearly relative thereto, first moving to the leftfrom its extreme telephoto position shown in FIG. 1 through the medianor intermediate position until it reaches the wide angle positionthereof. The member 1 also is adjustable relative to the members 2, 3and 4 for focusing for different object distances, and any focus of thezoom lens for any setting of the member 1 is correct for all zoomingpositions. During zooming, the member 2 is movable linearly relative tothe member 1 from its extreme telephoto position of FIG. 1 to itsextreme wide angle position of FIG. 3. A suitable lens mounting andzooming structure for the objectives disclosed herein is disclosed andclaimed in co-pending application Serial No. 854,732 filed November 23,1959, by F. W. Mellberg and assigned to the common assignee.

The front member 1 comprises a front biconvex, cemented doublet L --Land a rear singlet L predominantly convex forwardly and spaced closelyto the doublet L -L and having a dispersive internal contact surface RThe mean refractive index of the lens L exceeds that of the lens L Thelinearly movable negative zooming member 2 comprises a front negativemeniscus singlet L convex forwardly and a rear biconcave, cementeddoublet component L L predominantly concave forwardly. The doublet L Lhas a collective internal contact surface R and the mean refractiveindex of the lens L exceeds that of the lens L The stationary memher 3is a positive singlet L predominantly convex rearwardly, and forms anessentially afocal lens system with the members 1 and 2, it beingpossible to use this afocal system as an attachment or built in with theprime lens member 4 or with other prime lenses. The prime lens member 4behind the stop 5 includes a front positive singlet L predominantlyconvex forwardly, a biconcave singlet L predominantly concave forwardly,a positive meniscus singlet L concave forwardly and a rear biconvexsinglet L The lenses L to L have spherical surfaces or radii ofcurvature R to R axial thicknesses 2 to 1 and axial separations s to sThe separation s of the components L and L is sufficient to provideclearance for the stop 5 and a known filter member (not shown) which maybe selectively inserted into and removed from the space between thecomponents L and L The equivalent local length of the lens of FIG. 1 isvariable over at least a four to one range of magnification whilemaintaining a high degree of optical correction for a large aperture ofat least f/ 1.8 throughout the range.

A preferred example of a zoom lens forming one specific embodiment ofthe invention and having a magnification range of about four to one isconstructed in conformity with the following table wherein dimensionsare in terms of inches and the refractive indices for the sodium D lineand the Abbe dispersion numbers are respectively designated n and V:

Example I f/1.8. E.F.L.=1.277 telephoto; .Gisggrgedian; .3250 wideangle. B.F.L.=

R =+3.650 L t =.l00 na=l.75l. V=27.7

R =+1.310 L: h =.425 7Za=l.620 V=60.3

81 =.005 R4 =+1.465 L; t =.270 nd=1.620 V=60.3

.810 Telephoto s2 .555 Median .050 Wide Angle R6 =+5.0484 Li t4 =.060nd=1.617 V=55.0

R7 =+.5UG

8a =.l20 R5 =.674 L t =.055 na=1.620 V=60.3

Rn =+.568 L6 it =.150 na=1.75l V=27.7

.0503 Telephoto s1 .5547 Median .8089 Wide Angle R =+1.800 L t =.085nd=1.620 V=60.3

x5 =.280 R =+.390 La ts =.126 na=1.697 V=56.2

Ri4=Plano 8a =.080 R 5=.46D Lu t9 =.050 nd=1.751 V=27.7

Rn=+A00 81 =.D42 R17=.929 L t1u=.l05 nd=1.651 V=55.8

as =.007 R 9=+.7019 Ln t =.120 na=1.620 V=60.3

Rz0=.70l9

The zoom lens shown in FIG. 2 has lenses L ;-L and is very similar tothe zoom lens of FIG. 1 except that the zoom lens of FIG. 2 has aviewfinder prism L positioned between members 23 and 24 and in front ofstop 25. The zoom lens of FIG. 2 has spherical radii of curvature R to Raxial thisknesses to axial thicknesses t to t and axial separations s to5 The zoom lens of FIG. 2 is constructed in substantial compliance withthe following table in which dimensions are in terms of inches, ndesignates the indices of refraction for the sodium D line and V theAbbe dispersion numbers:

Example 11 //l.8. E.F.L.=l.402 telephoto; .7071 median; .3568 wideangle. B.F.L. =.475

R21=+3.650 L21 iz1=.l00 na=l.75l V=27.7

Rzz=+1.310 Ln l22=.425 1La=l.620 V=60.3

sat- .005 Rg =+l.465 L13 l13=.270 7Z4=L620 V=60.3

.810 Telephoto .m= .555 Median .050 Wide Angle R2e=+5.0484 Ln iz4=.060nd=1.617 V=55.0

.m=.120 Rzs= -,674 L15 tz5=.055 n=l.620 V=60.3

Rn=+.568 Lu t2q=.150 7L =1.75l V=27.7

R:n=+l0.761

.0503 Telephoto -m= .5547 Median .8089 Wide Angle R3i=+1.800 L11tz7=.085 nd=l.620 V=60,3

8z5=.027 Raa=Plan L iza=.405 nd=1.620 V=60.3

R; =Plano 8u=.288 R =+.434 Ln lzu=.137 11d=1.697 V=56.2

r:1=.085 Ra7= .506 L10 t:u=.054 nd=1.751 V=27.7

m=.043 R:9=1.010 L t i=.114 Tia- 1.651 V=55.8

8".005 Ru=+.760 Lu t3z=.135 'na=1.620

While the invention is thus described, it is not wished to be limited tothe precise details described, as changes may be readily made withoutdeparting from the spirit of the invention.

What is claimed is:

1. A zoom lens constructed substantially in accordance with thefollowing table in which dimensions are in terms of inches, andproceeding from front to rear L to L designate the lenses, R to R theradii of curvature of the surfaces, t to t the axial thicknesses, s; tos; the axial separations, n the indices of refraction for the sodium Dline and V the Abbe dispersion numbers:

h=.l00 n,1=l.75l V=-'.7 R:=+l.3l0

ti=.-t25 m=l.620 V=60.3 Rs= l5.-l00

81=.005 Ri=+lA65 L; [F270 n d=l.620 V=60.3

R =+l6J00 .810 Telephoto s1= 555 Median .050 Wide Angle Re=+5.0l8l L4t4=.060 7Ld=1.6l7 V=55.0

8a=.120 R5=.674 L l5=.055 n i=l.620 V=60.3

R9=+.5ll8 Ls t6=.l50 na=l.751 V=27.7

.0503 Telephoto s4= .5547 Median .8089 Wide Angle R F-H.800 L1 t1=.085na=l.620 V=60.3

85=.280 R 3=+.390 Ls 23=.l26 7La=l.697 V=56.2

Ri4=Plano 8e=.080 R 5=-.l60 Lo tg=.050 n=1.751 V=27.7

87=.042 Ri7=.929 L 0 tw=.l05 n=l.65l V=55.8

85=.007 R1e=+.70l9 L t1 =.120 na=1.620 V=60.3

2. A zoom lens conforming substantially to the following table in whichdimensions are in terms of inches, and proceeding from front to rear Lto L designate the lenses, R to R the radii of curvature of thesurfaces, t to [32 the axial thicknesses, r to s the axial separations,n the indices of refraction for the sodium D line and V the Abbedispersion numbers:

Rg =+3.650 Ln t2i=.100 'na=1.751 V=27.7

Rzg=+l.3l0 Lu t =A25 na=l.620 V=60.3

Rza=-l5.402 szi=.005 Rn=+L465 L21. tza=.270 na=l.620 V=60.3

.810 Telephoto 8iz= .555 Median .050 Wide Angle Ru=+5.0484 L14 t14=.060nd=L617 V=55.0

s2s=.l20 Ra =.674

tz5==.055 na=1.620 V=60.3 Rg9=+.568

lize=.150 'na=1.751 V=27.7 R; =+10.76l

.0503 Telephoto sz4= .5547 Median .8089 Wide Angle R3r=+1.800 L27tz7=.085 na=1.620 V=60.3

825=.027 Raa=PlanO In! Iz3=AO5 fld=1.620 V=60.3

- R 4=P1BI10 .m=.288 R:5=+.434 Ln tn=.137 nd=1.697 V=56.2

Rae=-16.700

871=.085 R37=.506 Lia t a=.054 na=l.751 V=27.7

82s=.043 R3 =-LO1O Lu tai=.ll4 na=1.651 V=55.8

.m=.005 R41=+.760 L31 t32=.135 'nd=1.620 V=60.3

No references cited.

